Residual Stress Improved by Water Jet Peening for A Quenched Gear

TRANSACTIONS OF MATERIALS AND HEAT TREATMENTVol.25 No.5PROCEEDINGS OF THE 14TH IFHTSE CONGRESSOctober 2004Residual Stress Improved by Water Jet Peening for A Quenched GearDong- Ying Ju', H. Tsuda, Vincent Jji', T. Uchiyama, R. Oba41. Department of Material Science and Engineering, Saitama Institute of Technology, Fusaiji 1690, Okabe,369-0293, Saitama, Japan2. Experiment and Analysis Dept, SUZUKI MOTOR Co, Hamamatsu -nishi, 1432-8611, Japan3. LM3, ENSAM University, 151, Boulevard de l'Hopital 75013, Paris, France4. High-Tech Research Center; Saiama Institute of Technology, JapanAbstract: In this paper, a running cost is cheap from the thing used for harmless peening treatment to the environment,health which an influence is rare in toward processing material like heat being only water fundamentally, and economical,and the characteristics is hard to get are given. There is some research about the residual stress improvement by water-jetpeening during the high-speed water. In this study, a big bubble cloud ceremony water-jet peening which dissolves theproblem of the form of the aplicable thing by exposing the whole of the applicable thing in the big bubble cloud as the wayof dealing with peening eficiently in a short time is proposed by this research. Moreover, the uniform compression residualstress is added around the surface of the processing side, and connected with the remarkable improvement of the faiguestrength of the part. Futermore, and safety processing is very pssible, and it thinks about the thing which has possiblehigh practical use, and wriers to get rid of the problems of the way of processing it with peening until now. Waterjetpeening was given by this research during high-speed water with big bubble cloud-type water toward tooth gearmanufactured by SCr420H3V2 to open the efet of water-jet peening during the high-speed water. A change was measuredat the time as the sutra of the residual stress on the surface of the test sttlement by the X-ray method, and the validity ofthis law was verified.Key words: Water Jet Peening, Residual Sress, Surface Improving, Quenched GearTHE normal cavitation often causes local height shockstrengthening mechanism in materials induced by waterpressure which reaches the level of GPa, so that thepeening process. Compressive residual stress inducedcavitation behavior might introduce damage on thby water peening has been used in evaluation for thesurface of machinery parts after long use duration [1-3].surface strengthening effect as a quantitativeOn the other hand, cavitation technology could beTherefore, not only on the surface but also at variousapplied in modifying the strength of materials surfacedepths of inside the material, the residual stress inducedas an attractive new peening technology. By inducingby water peening should be investigated. As a step tocavitation of ultrahigh speed water due to water-jet, thesolve these problems and furthermore to develop thenumerous impacts induced by the cavitation bubbleswater peening technique into industrial application, theimpact can produce compressive residual stress onresidual stresses introduced by water peening and heatmaterial surface in the similar way as that by shottreatment are investigated in this study.peening [4, 5]. Hirano et al. used the technique toIn the present paper, the residual stresses in a helicalrealize an improvement in thefatigue strength of agear of SCR420H carbon steel used in automobiles waspre-cracked specimen [6]. It has been verified that theinvestigated by X-ray diffraction. The residual stressescompressive residual stress can increase the fatigueon the surface and at various depths under the surfacelife of materials. Soyama et al. studied the optimumof the tooth of the gear were measured. Effect ofcavitation jet conditions during peening process ofpeening condition such as the peening time and heatSUS304 and SUP7 steel plates [7, 8]. The authorstreatment were investigated. Results of residual stressstudied a Carbon steel gear after water peening aninduced by water peening without and combining withclarified high level comprehensive stresses generatedheat treatment were compared. From the measuredon the surface of the gear [9-10]. However, there areresidual stresses, optimum condition of peening timestill some problems remain open in spite of theseand effctiveness of surface strengtheningreeffective results in above investigations. One point isdiscussed.that most of engineering parts are treated by thermalchemical process. Will the water peening technique be1. Experimentaleffective when the part has been processed by a heat1.1. Water Peening Equipmenttreatment? Will it be weaken for the water peeningThe schematic of the water jet equipment which caneffect after a heat treatment process? Is there anyjet ultahigh speed water bubble cloud with cavitationvariation of the optimum condition in the water peeningprocess for a heat treated part? Another problem is the中国煤化工igh pressur waterisa jet nozzle to the topMHCNMHGVol.25_ No.5TRANSACTIONS OF MATERIALS AND HEAT TREATMENT503of tank. The uniform big bubble cloud generated byheat treatment and then the residual stresses arewater jet collapse and produce impact on the surface ofmeasured.est piece in water. The detailed shape of the test1.3. Water Peening Methodspecimen is shown in Fig.2. The water is supplied by aIn water peening tests, the cavitation coefficient σ ispump to the water-jet from the reservoir tank with adefined as (Pz-P,)M(P1-P2). Here, P, P2 and Pv indicatecapacity 2.3m'. Here， the maximum pressure anthe jtting pressure of the nozzle, ambient pressure andvolume of water from the plunger pump aresaturated steam pressure, respectively. The dischargerespectively 30MPa and 16 litres /min. The temperaturepressure p1 of the water-jet was set as 30MPa. Aof the working water is kept in the range 20-24'C. Thedimensionless parameter x/d is defined as the actingjetting nozzle is installed in the center of thestandoff distance from the nozzle exit to the testvertical-type test water tank bottom through thespecimen. When the specimen is processed in thhigh-pressure hose.second peak area of the large uniform bubble cloud,1.2. Test Specimeneffective impact pressure achieves maximum value. InA helical gear as an automobile part was emppoyedthe case of peening treatment, the standoff distancein this research. Figure 3 showed the photograph of theparameter becomes nearby x/d=100. In order to choosegear after water peening. The material is SCr420Hthe most suitable peening time, various peening timescarbon steel which the carbon content is 0.2%. Thewere tested as Tp=5, 10, 30 and 60 minutes. Themain parameters of helical gear and mechanicalspecimen was fixed so that the gear cannot rotate, anproperties of the material are shown inwater-jet to the gear teeth was set in the dental rootinvestigated the effect of heat treatment,direction. In this case, it dealt with only one side of thecarburizing quenching was implemented to the gear.gear with peening.The specimens are processed by water peening after①①Reservoir tank②Feed pump③Plunger pump④④Test water tank⑤Test nozzle⑥Test specimen③00hZun ②血Fig. 1. Schematic of water-jet peening equipmentWaterjetpeening zoneO10 mmFig.2 Test specimenFig. 3T中国煤化工THCNMHGPROCEEDINGS OF THE 14H IFHTSE CONGRESSOctober 2004Table 1. Main parameters and properties of the gearmeasuring area 2. In the measuring area 4 near sideNumber of teeth2:edge of the tooth, the residual stress was measured atModule1.752mm from side line of the edges of the tooth avoidPressure angle18*measurement ificulty. In order to investigate theHelix angle30residual stress inside the tooth of the gear,Base circle diameter45.5148 mmeletropolishing was employed to polish. the surfaceYoung's modulus219.4 GPalayer with contolled current and speed. By this way,Poisson's ratio0.26the residual stress in point D on the surafce of a toothYield stress400 MPaof the gear shown in Fig. 5 at various depths wereHardness (Hv)180measured.Machine methodShaving1.4. Measurement Method of Residual Stress2. Results and DiscussionThe residual stresses induced by water-jet peening2.1. Estimation of Peening Areawere measured by X-ray difraction. The X-ray Gr KaBecause the specimen was submerged in waterradiation and a slit of 0.5mm were used in thebubble cloud, directly observing was almost impossible.measurement. The X-ray tube was operated at 40kVHowever it is very important to confirm the waterand 40mA. The diffraction plane was the (211)of aFecavitaion effect areaspecially for complex shape partsphase and the ifraction angle 20 was. 156.4 degree.in water-jet process. In this study, “'blue varmishX-ray was counted for 30 seconds using a positionmethod" was used, by which pre coated blue paintingsensitive proportional counter PSPC [1] at angle ofon surface of gear was examined to estimate theincidence Yo ranging from 0 to 45 degree. The stresscavitaion effect area. The exfoliated area of the bluefactor of the X-ray diffractionmethod was -318.71vamnish was regarded as the water-jet peening area byMPa/deg. The residual stress was calculated by the sin^cavitation effect. In other words, it can be determinedψ method, ie, the gradient of the line from the fivethat efect of peening treatment was made in thepoints on the 20- sin2 y diagram using minimium squareexfoliated bluevarnish area. The aspect of_ themethod. Here, y is the angle betweenthe normal line ofexfoliation of the blue varmish with peening time Tp: =5specimen surface and dffrction planes as shown inmin is shown in Fig.3. We could see blue varnishFig.4.exfoliated area covered the complete normal and sideFigure 5 shows the measured positions of residualsurface of the peening tooth together with area of thestress in a tooth of the helix gean. Because the toothdental roots. It is confirmed that water-jet peening hasshape of the helical gear is very complex, it istreated the whole surface of a complicated local toothrepresented as several measuring zone. Among. themas one selected zone. It suggestes that water-jet peeningareas 1,3 and 5 we)n the side plane of the tooth; andtreatment is ffecive for the helical gear. Furthermore,ofttooth. In theareas 2 and 4 were theby contolling rotation and movement of the axis of the，measuring areas 1 and 3, the residual stresses Ox and oygear, we could efectively treat the whole surface ofin the directions of the coordinate x and y. wereother complicated shape parts.measured. Due to the tooth interval of the gear is toonarrow, the residual stress σr can only be measured inX-ray tube」Water-jetVPSPCayringArca 24o,DMeasupiag Arcas20上σx。MeasuringArc年3 Measutg Arep ISurface of the specimenFig. 4. Coordinates for stress meaurement by XRD中国煤化工of rsidual sressesYHCNMHGVol.25 No.5TRANSACTIONS OF MATERIALS AND HEAT TREATMENT5052.2. Water Peening Results without Heat Treatmentuniformity of residual stresses after the water-jetFigure 6 presents the measured residual stresses σxpeening could lead to remarkable improvement on theand oy with water peening time on side surface of thefatigue strength of the gears. Water peening couldgear without heat treatment. We could see thatincrease compressive residual stress effectively afterdispersion of residual stress before waterjet peening (atheat treatment.Tp=0) due to machine processing was very obvious.Furthermore, as peening time increases from 30 toThere is remarkable tensile stress at point 4 and 5 near60 minutes, the uniformity of compressive stressestooth root and the difference of the residual stresses atimproves little, which suggests the saturated time forvarious positions is very large. After water-jet peening,stresses improvement ia about 30 minitues. In addition,he tensile stresses were improved into compressiveresidual stresses at the top of the tooth namelystresses and the residual stresses are improved inmeasuring point 1 changes lttle after water peening,almost all measurement points into compressivewhich is a specific point. The reason is the curvature atstresses about σx =500 MPa and σy =400 MPa after 60tooth top changes very complex. In this particular place,min treatment. As peening time increases from 10 to 60flow of jetted water leads to infinity from the viewpointminutes，the uniformity of compressive stressesof fluid mechanics. Due to decrease of local staticimproves lttle, which suggests there is a saturated timepressure on gear teeth and decline of the bubble cloudfor stresses improvement. Furthermore, the differenceimpact pressure, the effect of peening is hard to beof stresses can not be completely removed after a longbrought up.time treatment, which reveals exist of initial residual2.4. Residual Stresses at Various Depthsstresses generated in machinery process have influenceFigure 10 presents the measuring results of residualon improvement of residual stress by waterjetstresses at various depths of a teeth of the gearcavitation technology. This result corresponds with H.measured by X -ray diffraction. From Fig. 10(a), beforeSoyama's work on SUS304 plate in literature [7], inheat tratment, there is compressive residual stress atwhich he predicted that the tensile stresses have effect200 MPa or so in axial direction generated in the gearon the residual stress improvement.manufacturing process. The maximum compressive2.3. Residual Stresses on Tooth Surfacesteess is 280 MPa. After heat treatment, theThe results of residual stresses Ox on the toothcompressive stress achieves 300 MPa or so. Thsurafce of the gear induced by water peening aftermaxium on surface is 432 MPa. The thickness olquenching process are presented in Fig. 7. As thehardness layer is about 300 pum. After water peeningpeening increses, the compressive stress increase irand heat treatment, the residual stresses in axial andlevel. And after peening 60 minutes, the compressivetrangential direction are shown in Fig. 10(c). From theresidual stresses on tooth surface achieve about 700results, we could know, after water pening and heatMPa. The residual stresses 02 induced by water peeningtreatment, the maxmium axial and trangentialafter quenching process at various positions on thecompressive stresses achieve 870 and 710 MPa,tooth surafce are presented in Fig. 8. We could knowrespectively. The depth of the layer in whichthe compressive resdidual stresses achieve uniform oncompressive stresses are supperior to 400 MPa is nearlythe whole tooth surface after water peening combining100 um. It implies that after water peening, there is awith heat treatment.fairly thick and effive heardenning layer being notThe results of residual stresses σx and O, on thepolished which could improves the run-life greatly.Moreover, from Fig. 10(c), the depth of the layer inquenching process are presented in Fig. 9. After waterwhich compressive stresses are supperior to 300 MPa ispeening combining with heat treatment, thabout 500 pum. It implies that by water peening, thecompressive residual stresses achieve over 600 MPa.compressive stress region has been greatly increasedDuring water-jet peening, the level of compressiveinto the materials intermnal. And the compressiveresidual stresses increases as the peening time enlongs.stresses inside the meaterial are comparatively uniform,The residual stresses are improved in almost allwhich implies water peening could release themeasurement points into compressive stresses about 0xdispersion of residual stress due to machine processing.=700 MPa and O, =600 MPa after 60 minutes treatment.The measured results of residual streses showIn addition, the compresissive stress on tooth surfaceaccordance with that on the surafce of the gear by waterand side surface both reaches over 600 MPa, whichcavitation peening. The improvement of of residualverifies that when peening treatment is givenstreses verifies the effeciveness and efficiency of theeffectively, non-uniformity by the residual stress incaviation peening process.various directions will be eliminated and be lead tohomogenous distribution with compressive stress. The中国煤化工MYHCNMHG506PROCEEDINGS OF THB 14T IFHTSE CONGRESSOctober 2004800Tp=0m in5m in10m10m in60m in0-400量.---- .g -4000--- 0----=6--=--0.-800M easurng pointM easuring pont45(a) Residual stress σx in measuring area 1(b) Residual stress σy in measuring area 1Fig. 6. Change in residual stress distribution by water-jet peening for the specimen without treat treatment3Tp=0m in1m in- Left5m mM easurng PontM idde inE -20030m in-200400-400600曼600首..... .M easuring area 2M easuring Area 2Fig. 7. Change in residual stress with water peeningFig. 8. Distribution of residual stress σz on tooth surfacetime in area 2 for the specimen after treat treatmentof the gear after water peening 60 minutes12200M easuring point-1006◆Tp=0m in-3002”合-200合s500奉二1↑-600-900M easuring area 1(a) Residual stess σ x in area 1(b) Residual stresso y in area 10tM easuing area 5M easurng pohtM easuring area 5. Tp=0m in5min吕400&二二1omn中国煤化工5m in.MHCNMHG(c) Residual stess 0 x in area 5(d) Kesidual stress 0 y in area 5Fig. 9. Change in residual stress on side surface with water peening time of the specimen after treat treatmentVol.25 No.5TRANSACTIONS OF MATERIALS AND HEAT TREATMENT(1) When water peening was given efcively byDepth fom suftice δ. (um)water cavitation jet, high level compressive residual5100 .150200stresses on the surface of gear were generated up toabout -450MPa by merely water-jet peening and -700MPa by combining with quenching treatment.苦-200(2) The compresisstress on tooth surface andside surface of the gear both reaches over 600 MPa,which proved that the residual stresses are effectively重3 -600improved for an quenched gear.(3) It has confirmed that by water peening, the-800compressive stress region_ has been introducedincreased into the material. The compressive stressesResiualstess be fore heat treatn ent process- 1000inside the meateriarial are comparatively uniform, whichimplies that water peening could effectively improvethe dispersion of residual stresses due to machine(a) Residual stress before heat treatmentprocessing.。(4) Afer water peening inside. the gear, there is aDepth fom surfice δ, (um)fairly thick. and effive heardenning layer being not200 300 400 500 600polished which could improves the run-life greatly.0Acknowledgment+◆The support provided by the high tchnology resarch center县_000of Saitama Institute of Technology in arrying out this work isgratefully acknowledged.号-600References& -80CE. Brenne: Cavitation and Bubble Dynamics, OxfordResibualstess ater heat treata entUniversity Press, Oxford (1995).-10002 H. Kato: Cavitation, Maki Publishing, Tokyo, (1990), (in(6) Residual stress after heat treatmentJapanese).3 R.D. Hercamp and R.D. Hudgens: Cavitation CorrosionDepth from surface δ, (μm)Bench Test for Engine Coolants, SAE Tech. Paper Series6008001000881269, (1988).4 K. Sato, H. Soyama, Y. Yamauchi, T. Ikohagi, R. Oba and R.Oshima: Proc. of 11th Intemational Conference on JetCutting Technology, (1992), p.413.5 H.K. Tonshoff, F. Kroos and M. mann: Proc. of gAmerican Water Jet Conference, Houston Hart, TX (1995),-400一σ axilp.473是。trans.K. Hirano, K. Enomoto, E. Hayasi and K. Kurosawa:J Soc.Mater. Sci. Jpn. (in Japanese), VOol.45 (1996), p.740.00Res tlualstre sses after w ater peen ng and heat7 H. Soyama, J.D. Park, and M. Saka: J. Manufacturing Sci.and Eng. Trans. ASME, Vol.83 (2000), p.122.H. Soyama: JSME Int. Journal, Ser A, 45 (2000)0 p.173D.Y. Ju, T. Uchiyama, H. Machida, T. Kanawa, R. Oba, y.(C) Residual stress after water peening andheat treatmentSunayama, H. Tsuda, J.Mater. Sci, Forum, Trans. Tech. Pub,Vols.404 407. (2002), pp.635-640.Fig. l0. Distribution of residual stress at various depths0 H. Tsuda, D.Y. Ju, T. Uchiyama, Y. Sunayama, R. Oba,Residual Stress in a Quenched Gear Shaft Treated by Water3. ConclusionsCavitation Peening, J.Mater. Sci. Forum, (in print)In this paper, a helical gear of SCR420H carbon steel.11 Measurement of Stresses by X-ray, Society of Materialsprocessed by water cavitation peening combining withScience Japan, Yokendo, Ltd, (1990), p.80 (in Japanese).heat treatment. The residual stresses on the surface andinside of the tooth of the gear were measured withCorresponding author: ProfessorIDr. Dong Ying Ju,X-ray diffraction to evaluate the effect of the waterEmail: dyju@sitacjp.peening process. From the presented results, we canMail address Saitama Institute of Technology, Fusaiji 1690,obtain following conclusions:中国煤化工93, Sitama, Japan,YHCNMH G